Submitted to: International Congress of Plant Pathology Abstracts and Proceedings
Publication Type: Other
Publication Acceptance Date: July 20, 2002
Publication Date: February 20, 2003
Citation: OKUBARA, P.A., LANDA, B.B., KORNOLEY, J.K., PAULITZ, T.C. WHEAT RHIZOSPHERE-MICROBE INTERACTIONS--FACTORS AND GENES. INTERNATIONAL CONGRESS OF PLANT PATHOLOGY ABSTRACTS AND PROCEEDINGS. v. 2. p. 205. 2003. Technical Abstract: Host genes are likely to have important roles in interactions with both root pathogens and beneficial soil microbes that suppress such pathogens. Triticum aestivum (hexaploid wheat) has limited genetic resistance to the necrotrophic fungal pathogens Pythium, Rhizoctonia, Gaeumannomyces, and Fusarium. However, disease severity is attenuated by rhizosphere biological control agents, including Pseudomonas fluorescens, that colonize host roots and exert antifungal action through a variety of mechanisms. The goal of our research is to understand the molecular pathways within wheat that govern the three-way interaction between host, pathogen and biological control agent. Cultivar-specific rhizosphere interactions have been reported in wheat and tomato. To explore natural variation in Pacific Northwest wheat, we have surveyed cultivars of T. aestivum for the ability to sustain root colonization with the aggressive P. fluorescens strain Q8r1, as compared to Q2-87, a weaker colonizer. We report that five cultivars, Boundary, Edwin, Finley, Lambert, and Stephens, supported higher levels of Q8r1 than Q2-87. In some cases, colonization by Q8r1 was accompanied by an inhibition of root growth, possibly due to the phytotoxic effects of the antifungal metabolite 2,4-diacetylphloroglucinol. Differences in root morphology were observed among the cultivars tested, but the ability to undergo colonization by Q8r1 was not correlated to any single root morphometric parameter. Current data on pathogen suppression, 2,4-DAPG phytotoxicity, and expression of defense response genes in roots will be discussed.